1) Field of the Invention
This invention relates to a gas turbine which uses a coolant such as air and steam for cooling a dynamic blade. More specifically, this invention relates to a joint structure of a coolant flow passage in the gas turbine for coupling a flow passage for supplying a coolant from a rotor disk to the dynamic blade, a tube seal and the gas turbine.
2) Description of the Related Art
In order to increase thermal efficiency in the gas turbine, a technique in which steam is used as a coolant instead of the air, to cool hot members such as a dynamic blade, a rotor disk or a stationary blade of the gas turbine is now being used. This is due to the following reasons. That is, the specific heat at constant pressure of dry steam is cp=1.86 kJ/kgK under a standard condition, which is a value almost twice as large as the specific heat at constant pressure of the air, cp=1.00 kJ/kgK. Therefore, the steam has a large heat capacity as compared with the air of the same mass, and the endothermic effect thereof increases. Further, if the wet steam is used as a coolant, latent heat of vaporization of the wet portion can be used for cooling, and hence the endothermic effect thereof further increases. Therefore, when the steam is used for the coolant, the cooling efficiency can be increased than using the air, and hence the temperature of the combustion gas at the entrance of the turbine can be set high. As a result, the thermal efficiency can be improved.
In the conventional air cooling, air from the compressor has been used as a coolant for the dynamic and stationary blades of the turbine. However, if this compressed air is used for cooling, the work that can be taken out from the turbine decreases. Here, if steam is used instead of the air, the cooling air for the dynamic and stationary blades can be saved, and hence the work that can be recovered by the turbine increases by this amount, thereby the work that can be taken out from the turbine can be increased.
FIG. 8 is a cross section which shows a steam flow passage for supplying cooling steam to the dynamic blade of the turbine. The steam supplied to the hollow main spindle 800 of the turbine is guided to a steam supply pipe 801 heading radially outwards. Thereafter, this steam flows into a steam supply pipe 804 which goes axially through the vicinity of the outer periphery of a rotor disk 803, and is supplied to a cooling flow passage (not shown) provided inside of the dynamic blade 805.
FIG. 9 is a cross section which shows a joint structure of the coolant passage, which has been conventionally used for supplying or recovering the cooling steam from the rotor disk side to the dynamic blade side. As shown in this figure, the end 121 of the joint section 120 is formed into a spherical shape, and fitted into a coolant passage inlet 805a of a dynamic blade 805, which is also formed into a spherical shape to fit in with the end. A protruding portion 120a is peripherally provided at the other end of the joint section 120. When the other end of the joint section 120 is inserted into the coolant passage outlet 803a on the rotor disk 803 side, the top of the protruding portion 120a and the coolant passage outlet 803a abut against each other, which becomes a seal point 125 to prevent leakage of the coolant.
In Japanese Patent Application Laid-Open No. 2000-274261, there is disclosed a joint structure of a cooling passage, wherein a flange is formed at one end of a joint section, and inserted into a groove having the same cross section as that of the flange, provided at the root of a dynamic blade, to thereby connect a coolant flow passage. A spherical spring is provided at a portion where this joint portion is inserted into a cooling flow passage outlet formed in a rotor disk, and leakage of steam is prevented by the elastic force of this spring.
The end 121 of the joint section 120 is spherical and comes into face contact with a coolant inlet 805a of the dynamic blade 805 formed into a spherical shape which fits in together with the end, to prevent the steam from leaking. However, it is difficult to increase the machining accuracy of the face, and steam leaks slightly from this portion. Further, during operation of the gas turbine, the temperature of the joint structure portion of the cooling flow passage increases up to about 400xc2x0 C. Therefore, the joint section 120 is manufactured from a metal material, and inserted into the coolant passage outlet 803a of the rotor disk 803 manufactured from a metal material as well. Therefore, a gap is always formed at the seal point 125, causing a problem in that steam leaks from this gap. Since the amount of leakage of the steam is not so large, it is not a big problem so far. However, in order to increase the use efficiency of the steam, it is necessary to minimize the steam leakage in the seal portion.
The joint structure of a cooling passage disclosed in Japanese Unexamined Patent Publication No. 2000-274761 can correspond to the radial movement of the rotor disk. However, when a movement in the direction perpendicular to this radial direction occurs, if the movement is very small, this joint structure can correspond thereto, but if the movement is large, a gap is formed between the flange and the root of the dynamic blade, and hence causing a problem in that steam leaks from this gap.
It is an object of this invention to provide a joint structure of a cooling flow passage and a tube seal in a gas turbine, and a gas turbine, wherein wastage of steam is suppressed by reducing leakage of the steam, and even if the dynamic blade and the rotor disk move relative to each other, the seal performance can be maintained.
The joint structure of a coolant passage in a gas turbine according to one aspect of the present invention comprises a rotor disk having a first coolant passage port for supplying or recovering a coolant to or from a dynamic blade, the dynamic blade being fitted to the outer periphery of the rotor disk, a second coolant passage port provided at the root of the dynamic blade, and a tube seal having a tubular barrel, the end of the barrel inserted into the second coolant passage port being formed into a spherical shape, and the side of the barrel inserted into the first coolant passage port being provided with an elastic member which deforms in the radial direction of the barrel. The internal surface of the second coolant passage port and the spherical end of the tubular barrel come in line contact with each other.
Thus, the spherical end of the tube seal and the internal surface of the coolant passage port provided at the root of the dynamic blade into line contact with each other, to thereby suppress leakage of the coolant in this portion. At the coolant passage port on the rotor disk side, leakage of steam is suppressed by the spherical elastic member such as a spring provided on the tube seal barrel. Since the coolant passage port provided in the dynamic blade and the end of the tube seal barrel are brought into line contact with each other, leakage of the coolant can be suppressed, even if the machining accuracy in this portion is not so high. Further, in the coolant passage on the rotor disk side, the seal performance is maintained by the elastic member, and vibrations can be absorbed by a damping action of this elastic member. Therefore, stable sealing effect can be maintained not only on the rotor disk side but also in the coolant passage on the dynamic blade side.
Since the end of the tube seal barrel is formed into a spherical shape, it endures large centrifugal force acting thereon due to the rotation of the rotor disk, and the seal performance of this portion can be maintained. Even when the dynamic blade and the rotor disk shift from each other and the tube seal inclines, the seal performance can be maintained by the spherically formed end of the tube seal barrel and the elastic member provided on the tube seal barrel. At this time, since the shift of the dynamic blade is absorbed by the inclination of the tube seal, a larger shift can be absorbed than by a horizontal shift of the tube seal in the radial direction. By these actions, with this joint structure, the seal performance is maintained regardless of the operation condition, to suppress the amount of coolant such as steam or air leaking from the joint portion of the cooling flow passage. Therefore, the coolant is effectively used, and the thermal efficiency of the gas turbine can be also improved. The joint structure of the cooling flow passage is applicable to either a gas turbine using steam as the coolant or a gas turbine using air.
As the means for bringing line contact, there can be mentioned forming a spherical face having a larger curvature than that of the spherical end of the tube seal into a concave shape on the internal surface of the coolant passage port provided at the root of the dynamic blade, or forming the internal surface of the coolant passage port into a convex spherical shape, so that these abut against the spherical end of the tube seal. Further, a ring having an inner diameter smaller than the outer diameter of the spherical end of the tube seal may be provided between the end of the tube seal and the inside of the coolant passage provided at the root of the dynamic blade, to bring the inner periphery of the end of this ring and the spherical end of the tube seal into line contact with each other. Further, the inside of the coolant passage provided at the root of the dynamic blade may be formed step-wise, and the small diameter section thereof is made smaller than the outer diameter of the spherical end of the tube seal, to thereby bring the end of the tube seal and the small diameter section of the coolant passage into line contact with each other.
The joint structure of a coolant passage in a gas turbine according to another aspect of the present invention comprises a rotor disk having a first coolant passage port for supplying or recovering a coolant to or from a dynamic blade, the dynamic blade being fitted to the outer periphery of the rotor disk, a second coolant passage port provided at the root of the dynamic blade, the second coolant passage port having an internal surface that is conical such that it tapers towards the end of the dynamic blade, and a tube seal having a tubular barrel, the end of the barrel inserted into the second coolant passage port being formed into a spherical shape, and the side of the barrel inserted into the first coolant passage port being provided with an elastic member which deforms in the radial direction of the barrel.
Thus, the spherical end of the tube seal barrel to abut against the coolant passage port, whose inner surface provided in the dynamic blade being formed into a conical shape, to thereby suppress leakage of the coolant in this portion. At the coolant passage port on the rotor disk side, leakage of steam is suppressed by the spherical elastic member such as a spring provided on the tube seal barrel. Since the coolant passage port provided in the dynamic blade and the end of the tube seal barrel are brought into line contact with each other, leakage of the coolant can be suppressed, even if the machining accuracy in this portion is not so high. Further, since the coolant passage port provided at the root of the dynamic blade is formed into a conical shape, machining is easy, and much labor is not necessary for manufacturing.
The joint structure of a coolant passage in a gas turbine according to another aspect of the present invention comprises a rotor disk having a first coolant passage port for supplying or recovering a coolant to or from a dynamic blade, the dynamic blade being fitted to the outer periphery of the rotor disk, a second coolant passage port provided at the root of the dynamic blade, the second coolant passage port having an internal surface that is conical such that it tapers towards the end of the dynamic blade, and a tube seal having a tubular barrel, a working face being formed on the outer periphery of the end of the barrel inserted into the second coolant passage port, the side of the barrel inserted into the first coolant passage port being provided with an elastic member which deforms in the radial direction of the barrel, and a protruding portion which restricts a radial movement of the barrel, by abutting against at least one of the internal surfaces of the first and the second coolant passage ports, being provided on the side of the barrel.
The joint structure of the cooling flow passage suppresses leakage of the coolant by bringing the working face formed on the outer periphery of the end of the barrel to abut against the internal surface of the coolant passage port provided in the dynamic blade, whose inner face is formed into a conical shape. Further, leakage of the coolant in the coolant passage port provided in the rotor disk is suppressed by the elastic member. The radial movement of the tube seal is also restricted by the protruding portion provided in the tube seal barrel, to thereby prevent the elastic member from being damaged. This joint structure serves the function effectively, when the shift between the dynamic blade and the rotor disk is small. However, when the shift of the dynamic blade is large, the inclination of the tube seal increases, to cause leakage of the coolant in the end where the working face is formed. Therefore, it is desirable to apply this joint structure when the shift of the dynamic blade is small. In this tube seal, since it is not necessary to form the end thereof into a spherical shape, manufacture is easy, and the manufacturing cost can be reduced.
The working face formed on the outer periphery of the tube seal barrel includes one formed with a curved surface or one having a cut instead of the curved surface. Alternatively, this portion may be formed into a conical shape matched with the shape of the internal surface at the coolant passage port provided in the dynamic blade. However, the shape other than the curved surface will come in face contact with the internal surface of the coolant passage port provided in the dynamic blade, and hence it is desired to form the shape into a curved surface from the viewpoint of the seal performance.
In the tube seal according to still another aspect of the present invention, its end is formed into a spherical shape, and the side of the barrel inserted into a coolant passage port to be coupled is provided with an elastic member that deforms in the radial direction of the barrel. Since the end of this tube seal is formed into a spherical shape, even if a large force acts thereon in the axial direction of the tube seal, it can endure the force to maintain the seal performance. The seal performance can be also ensured by the elastic member that deforms in the radial direction of the barrel. Even when the tube seal is inclined, the seal performance can be maintained by the spherical end and the elastic member, and hence, the sealing effect can be exhibited even in a portion where the shift of the tube seal with respect to the radial direction is large.
The gas turbine according to still another aspect of the present invention comprises a compressor, a combustor, and the joint structure explained above.
In this gas turbine, the rotor disk and the dynamic blade are coupled by the joint structure of the cooling flow passage, to supply and recover the coolant to and from the dynamic blade. The dynamic blade and the rotor disk of the gas turbine reach high temperatures, and are exposed to a high centrifugal force, and hence the dynamic blade and the rotor disk may be shifted from each other due to thermal deformation, and a large force acts on the sealing structure. Since the joint structure applied to this gas turbine seals the coolant passage by bringing the tube seal, whose end being formed into a spherical shape, into line contact with the inner surface of the coolant passage, even if a high centrifugal force acts thereon, the sealing effect can be maintained. Further, even if the dynamic blade is shifted, the tube seal exhibits the sealing effect, while being inclined by the spherical end and the elastic member provided on the barrel of the tube seal, to absorb the shift. In this manner, even under high temperatures and under an environment where a high centrifugal force is acting, wastage of the coolant can be made as small as possible by the stable sealing effect, and the thermal efficiency of the gas turbine can be improved.
These and other objects, features and advantages of the present invention are specifically set forth in or will become apparent from the following detailed descriptions of the invention when read in conjunction with the accompanying drawings.